The present invention relates to a detecting circuit and a circuit detecting method, and more particularly to a detecting circuit for detecting a connecting condition of an external terminal circuit, and a method thereof.
Universal Serial Bus (USB) is a standard interface for connecting peripheral devices to a host computer. For USB 3.0, the USB 3.0 receivers terminate the transmission line by placing a small resistor to ground. Transmitters will check for this termination resistor on the receiver as a way for detecting the presence of a USB 3.0 receiver. In some cases, however, receivers may terminate the transmission line by placing the small resistor to the supply voltage rather than ground when coupling the receivers to the transmitters. When this happens, the transmitter may fail to detect the presence of the small resistor. Therefore, there is a need to improve the conventional methods for different situations in order to precisely detect the presence of the termination that is not conformed to USB 3.0 standard and make the transmitter compatible with different receiver specifications.